1. Field
Apparatuses and methods consistent with the exemplary embodiments relate to a collision avoidance assistance technology for a vehicle such as an automobile, and more particularly to a device for avoiding collisions between a traveling vehicle and an animal.
2. Description of Related Art
In the field of the driving assistance technology for a vehicle such as an automobile, various configurations are proposed for a system that monitors the area ahead of a traveling vehicle using an on-vehicle video camera or a radar sensor and, when an object such as other vehicles, a person, or an animal is detected, predicts the possibility of collision with the object to assist the driver in avoiding collision with the object. For example, Japanese Patent Application Publication No. 2010-020401 (JP 2010-020401 A) and Japanese Patent Application Publication No. 2010-108507 (JP 2010-108507 A) disclose a configuration that determines whether an object detected in an image, captured by the on-vehicle camera, is a person or a tetrapod. If the detected image is the image of a tetrapod, the configuration estimates the tetrapod's presence area after the movement of the tetrapod, considering that the tetrapod is most likely to move in the direction of its head. Then, the configuration determines whether the estimated tetrapod's presence area overlaps with the vehicle's future presence area to detect the possibility of collision.
Japanese Patent Application Publication No. 2009-301283 (JP 2009-301283 A) proposes a configuration that, when there is a possibility of collision with an object, changes the frequency and the time, at which the possibility of collision is notified, between the case where the object is a person and the case where the object is a tetrapod. In addition, for the method for recognizing whether an object detected in a captured image is a tetrapod, Japanese Patent Application Publication No. 2010-113550 (JP 2010-113550 A), Japanese Patent Application Publication No. 2010-092429 (JP 2010-092429 A), and Japanese Patent Application Publication No. 2010-009372 (JP 2010-009372 A) propose a configuration that determines whether the object is a tetrapod by determining whether the angle of the vector indicating the posture of the image of the object changes periodically (Japanese Patent Application Publication No. 2010-113550 (JP 2010-113550 A)), by determining whether the image element corresponding to the motion of the legs changes in the configuration of the lower part of the image of the object (Japanese Patent Application Publication No. 2010-092429 (JP 2010-092429 A)), or by determining whether the image of the object has an image element corresponding to the backbone and the four legs of a tetrapod (Japanese Patent Application Publication No. 2010-009372 (JP 2010-009372 A)).
In general, animals (for example, livestock such as a horse, ox, and sheep and wild animals such as a deer, wild goat, bear, kangaroo) that may enter the traveling road of a vehicle differ in the behavior pattern or the behavior characteristics according to the type. For example, the behavior of an animal when a vehicle approaches the animal depends on the type of the animal; the animal runs away (flees) from the vehicle, stands transfixed where the animal is, approaches the vehicle, or runs into the traveling road. The moving speed and the moving direction of the animal also differ among animal types. Therefore, when an animal is detected in the image of the traveling road in the traveling direction of the vehicle or in the image of its surroundings, the type of the animal must be identified; otherwise, it is difficult to estimate where the animal will move after it is detected, that is, the position where the animal will exist or the area where the animal is likely to exist in the future. In addition, it may become difficult to accurately determine the possibility of collision between the vehicle and the animal. On this point, if the object is an animal and if the type of the animal is not identified and the tendency of the behavior cannot be predicted, it is not known in which direction and at what speed the image of the animal in the captured image will move. Therefore, in predicting the animal's future presence area, it may become necessary to understand the tendency of the behavior of the animal or to make an image analysis of a relatively large area in the image for tracking the image of the animal. However, because the image information is four-dimensional information having the two-dimensional coordinate values, brightness, and time, the calculation load and the processing time are significantly increased as the analysis range of the image area becomes larger. This means that the quick implementation of collision possibility determination and collision avoidance assistance requires higher-performance calculation processing device and memory, resulting in an increase in the cost.
In addition, when the behavior characteristics of animals differ among animal types, efficient assistance for collision avoidance also differs among animal types. When a warning by sound and light is issued to an animal detected ahead of the vehicle, the reaction differs among animal types; some animals are highly sensitive to the warning and move away from the vehicle and some other animals do not react to the warning at all and enter the traveling road with little or no change in the behavior. In particular, in the former case, collision can be avoided by issuing a warning by sound or light with no need to apply the brake or to perform a steering operation on the vehicle. In the latter case, collision can be avoided by applying the brake or by performing the steering operation on the vehicle. Conversely, when collision can be avoided only by issuing a warning, driving assistance by applying the brake or by performing the steering operation on the vehicle is not necessary. Similarly, when collision can be avoided by applying the brake or performing the steering operation on the vehicle, the generation of a warning is not necessary. Therefore, when an animal is detected as an object in the image of the traveling road in the traveling direction of the vehicle or in the image of its surroundings, it is preferable that assistance for collision avoidance be provided in a more suitable mode according to the type of the animal.